Hybrid on the hard shoulder

Toyota has begun an investigation into why its Prius petrolelectric hybrid cars might be stalling or shutting off, sometimes at motorway speeds.

No such incidents are believed to have stricken UK drivers, but 13 cases have been reported to the US National Highway Traffic Safety Administration, according to the car maker.

A Toyota GB spokesman said it was too soon to know what might be going wrong with the vehicles, which are capable of more than 65mpg, but US dealers are reported to be pointing the finger at a software problem.

The family-sized Prius is the most fuel-efficient car on the market according to standard European drive-cycle testing, beating even the smallest cars. But while many automotive industry analysts regard the Prius as reliable, some believe the extra cost and complexity of hybrids will limit their market appeal.

Prius’s hybrid drive system relies on sophisticated computer control to maximise the efficiency of its combination of 1.5-litre petrol engine and 50kW electric motor; the two units can drive the car jointly or independently, and batteries are kept charged by engine power and energy recovered through regenerative braking.

Fewer than 10,000 Priuses were sold in Europe last year, but in the US, where petrol prices are at record highs and diesel cars are unpopular, nearly 54,000 have been sold — more than twice the 2003 level. Sales could reach 100,000 this year, about half the total expected US hybrid market, according to analyst JD Power-LMC.

Next year Toyota will start producing a hybrid version of its Camry saloon for the US market at its factory in Kentucky, and hopes to turn out 4,000 vehicles per month. Europe will continue to be supplied with hybrids made in Japan.

Toyota’s luxury Lexus brand will put a hybrid on sale in Europe on 15 June. The RX400h features a similar hybrid system to the Prius, but with a 3.3-litre V6 engine.